Mapping probe system for neuromuscular electrical stimulation apparatus

ABSTRACT

A monopolar neuromuscular electrical stimulation (NMES) apparatus is configured for use with a cannula and a remote electrode. The apparatus includes a longitudinally rigid rod that is movable in the cannula throughout a range of operative positions in which inner and outer end portions of the rod extend longitudinally outward from the inner and outer ends of the cannula. The apparatus further includes a single electrode configured to be supported as a solitary electrode on the inner end portion of the rod for movement with the rod through the cannula. In this manner, the electrode can be moved into and out of contact with internal test sites to apply NMES at the internal test sites in an electrical circuit with the remote electrode upon movement of the rod back and forth in the cannula. Additionally, the rod is a rigid tube and the electrode is a suction-tip electrode configured to communicate pneumatically with the rigid tube.

RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 10/897,213, filed Jul. 21, 2004, which claims the benefit ofprovisional U.S. Patent Application No. 60/489,447, filed Jul. 23, 2003.Both prior applications are incorporated by reference.

TECHNICAL FIELD

This technology relates to the field of neuromuscular electricalstimulation.

BACKGROUND

Neuromuscular electrical stimulation (NMES) involves the controlledstimulation of muscular nerve centers. Known uses of NMES include, forexample, the diagnosis of chronic pelvic pain and the installation of asystem to produce an effective cough mechanism.

It may be desirable to use minimally invasive surgical techniques forNMES. A minimally invasive NMES apparatus 10 that is known in the priorart is shown schematically in FIGS. 1 and 2. This apparatus 10 includesthe cannula portion 12 of a trocar system. The cannula 12 is shown in anoperative position in which it extends through an incision 15 in apatient's abdominal wall 16 to communicate the internal peritoneal space19 with the adjacent external space 21 in the operating room. A trocar(not shown) is first moved through the cannula 12 and pressed againstthe outer surface of the abdominal wall 16 to form the incision 15 in aknown manner. The cannula 12 is then advanced through the incision 15.The apparatus 10 further includes a mapping probe system 30 which isshown in an operative position extending through the cannula 12 from theexternal space 21 into the peritoneal space 19.

The mapping probe system 30 includes a rigid metal tube 32 which isinserted through the cannula 12 after the trocar is withdrawn from thecannula 12. A flexible plastic tube 34 is then inserted through therigid metal tube 32. The inner end of the flexible tube 34 is equippedwith a contact electrode 36. The outer end of the flexible tube 34 isconnected to an operating room vacuum.

As shown in FIG. 2, the electrode 36 is a suction tip electrode.Accordingly, it has an internal passage 37 that serves as a suction port37 to enable suction in the flexible tube 34 to hold the electrode 36temporarily against an internal surface at a test site, e.g., a phrenicnerve motor point on the diaphragm muscle. An electrical wire 38 in theflexible tube 34 is part of a known stimulator system that connects theelectrode 36 in a pair with a remote electrode (not shown) to provideNMES for characterization and mapping of the electrical response at theinternal test site.

As known in the art, the patient's abdomen is inflated by gas pressureprovided in the peritoneal space 19. As further known in the art, thecannula 12 grips the rigid tube 32 to form a pneumatic seal that blocksleakage of the inflation gas along a path extending outward through thecannula 12 between the outer surface of the rigid tube 32 and thesurrounding inner surface of the cannula 12. The rigid tube 32 is rigidenough to withstand the grip of the cannula 12 without collapsing, butthe flexible tube 34, which can bend under the influence of the movingdiaphragm muscle, is not. As shown in FIG. 2, a small gap exists betweenthe outer surface 42 of the flexible tube 34 and the surrounding innersurface 44 of the rigid tube 32. This gap provides a flow path thatenables the inflation gas to leak from the peritoneal space 19 withoutpassing through the suction-tip electrode 36.

SUMMARY

A monopolar neuromuscular electrical stimulation (NMES) apparatus isconfigured for use with a cannula and a remote electrode. The apparatusincludes a longitudinally rigid rod that is movable in the cannulathroughout a range of operative positions in which inner and outer endportions of the rod extend longitudinally outward from the inner andouter ends of the cannula. The apparatus further includes a singleelectrode configured to be supported as a solitary electrode on theinner end portion of the rod for movement with the rod through thecannula. In this manner, the electrode can be moved into and out ofcontact with internal test sites to apply NMES at the internal testsites in an electrical circuit with the remote electrode upon movementof the rod back and forth in the cannula. Additionally, the rod is arigid tube and the electrode is a suction-tip electrode configured tocommunicate pneumatically with the rigid tube.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a prior art NMES apparatus including amapping probe system.

FIG. 2 is a sectional view of parts of the mapping probe system of FIG.1.

FIG. 3 is a sectional view of parts of a mapping probe system developedby the inventors.

FIGS. 4 and 5 are views which are similar to FIG. 3, and which showadditional parts of the mapping probe system of FIG. 3.

FIG. 6 is a schematic view of parts of another mapping probe systemdeveloped by the inventors.

FIG. 7 is an enlarged, partly sectional view of parts of the mappingprobe system of FIG. 6.

DETAILED DESCRIPTION

FIGS. 3-7 show mapping probe systems with parts that are examples of theelements recited in the claims. FIG. 3 thus shows a mapping probe system50 including a rigid rod 52. The rod 52 is receivable through thecannula 12, and is movable longitudinally within the cannula 12throughout a range of operative positions in which it extends outwardfrom the opposite ends of the cannula 12 in the manner shown in FIG. 1.More specifically, the rod 52 is long enough for an outer end portion 54of the rod 52 to extend from the cannula 12 into the operating roomspace 21 sufficiently to be grasped and manipulated manually by asurgeon, and for an inner end portion 56 simultaneously to extend fromthe cannula 12 into the peritoneal space 19 sufficiently to reach aplurality of internal test sites.

The rod 52 can be made of plastic, metal, a composite material, or anyother suitable material. By “rigid” it is meant that the rod 52 willretain a linear or substantially linear configuration centered on alongitudinal central axis 57 when subjected to bending stresses that areordinarily applied manually during use. Preferably, the rod 52 as awhole is rigid enough not to bend under its own weight when supportedfrom only one end, although it may have a small range of elasticdeformation to and from a slightly bowed configuration. Importantly, therod 52 is rigid enough to withstand the pneumatically sealing grip ofthe cannula 12 without collapsing.

This particular example of the rod 52 is a cylindrical tube as shown inFIG. 3. The outer diameter of the tube 52 is predetermined withreference to the cannula 12 for establishment of the pneumatic sealbetween the outer surface 58 of the tube 52 and the surrounding innersurface of the cannula 12.

The terminal outer end 70 of the tube 52 is connectable to the operatingroom vacuum. An internally threaded metal sleeve 72 is installed at theterminal inner end 74 of the tube 52. A contact electrode 76 has acontact portion in the form of a stainless steel ball tip 78 which iscentered on the axis 57, and further has an externally threaded metalstem 80 which is screwed into the metal sleeve 72. The ball tip 78 isreceivable through the cannula 12 with the tube 52. As shown in FIG. 3,the diameter of this particular ball tip 78 is equal to the outerdiameter of the tube 52. An electrically non-conductive sleeve 82 isreceived over the stem 80 and extends axially from the ball tip 78 tothe metal sleeve 72.

An insulated electrical wire 90 has an uninsulated portion 92 in contactwith the metal sleeve 72. The wire 90 extends outward through apneumatically sealed aperture 95 in the outer end portion 54 of the tube52 for connection of the electrode 76 in the stimulator system. Anoptional metal stand-off hinge 96 (FIG. 4) with an additional metalsleeve 98 may be interposed between the ball-tip electrode 76 and themetal sleeve 72 on the tube 52. The mapping probe system 50, whenequipped with the ball-tip electrode 76, enables the surgeon initiallyto coarse map an internal region by sliding the rigid tube 52longitudinally back and forth within the cannula 12, and thereby to movethe ball tip 78 of the electrode 76 into and out of contact withinternal test sites in the region being mapped. The surgeon cansubsequently map the same region (or a different region) further withthe suction-tip electrode 100 shown in FIG. 5.

The suction-tip electrode 100 is part of an electrode assembly 102 thatis interchangeable with the ball-tip electrode 76 at the inner end 74 ofthe rigid tube 52. The electrode assembly 102 includes a cylindrical,flexible plastic tube 104 with inner and outer ends 106 and 108. Likethe ball tip electrode 76, the suction tip electrode assembly 102 ismovable through the cannula 12 and into the peritoneal space 19 with theinner end portion 56 of the rigid tube 52. A wire 120 within theflexible tube 104 electrically connects the suction-tip electrode 100 atthe inner end 106 of the tube 104 with a tubular metal connector 122 atthe outer end 108 of the tube 104. An externally threaded stem 124 onthe connector 122 can be screwed into the internally threaded sleeve 72at the inner end 74 of the rigid tube 52. This connects the suction-tipelectrode 100 with the rigid tube 52 both electrically andpneumatically.

By “flexible,” as opposed to “rigid,” it is meant that the flexible tube104 is not rigid enough to withstand the pneumatically sealing grip ofthe cannula 12. The flexible tube 104 can bend between its opposite ends106 and 108 under stresses ordinarily applied manually by the surgeonand/or the moving diaphragm muscle during use, but is preferably able toreturn elastically to an original, unstressed condition having a linearor substantially linear configuration. The mapping probe system 50, whenequipped with the electrode assembly 102, defines a suction air flowpath that extends through the flexible tube 104 from the suction-tipelectrode 100 to the connector 124, and further through the rigid tube52 from the connector 122 and the sleeve 72 to the vacuum source at theouter end 70 of the rigid tube 52. The system 50 is free of a leakageflow path along which the abdominal inflation gas can escape theperitoneal space 19 without passing through the suction-tip electrode100.

Parts of an additional mapping probe system 150 are shown schematicallyin FIGS. 6 and 7. This system 150 also includes a rigid rod in the formof a tube 152 that is receivable and movable in the cannula 12throughout a range of operative positions like the operative positionshown in FIG. 1. At the inner end of the tube 152 is an internallythreaded sleeve 154 which, while preferably having the sameconfiguration as the sleeve 72 described above, may be formed of eitherelectrically conductive or electrically non-conductive material. Otherparts of the system 150 include a bi-polar electrode assembly 156 and amanually operated laproscopic instrument 158 with a scissor-actionhandle 160.

The electrode assembly 156 has an externally threaded sleeve portion 170(FIG. 7) that is screwed into the internally threaded sleeve 154 at theinner end of the rigid tube 152. When the electrode assembly 156 ismounted on the tube 152 in this manner, it is receivable through thecannula 12 with the tube 152, and is thus movable into and within theperitoneal space 19 with the tube 152.

An outer end portion 172 of the tube 152 is fitted tightly into a barrelportion 174 of the instrument 158. The barrel 174 blocks the abdominalinflation gas from escaping through the outer end of the tube 152. Adrive rod 178 extends from the handle 160 of the instrument 158 throughthe barrel 174 and the tube 152 to a linkage 190 in the electrodeassembly 156. The drive rod 178 moves axially to actuate the linkage 190in accordance with manual manipulation of the handle 160.

The pivotal arms of the linkage 190 include two arms 192 and 194 withelectrically uninsulated outer end portions 196 and 198. Those portions196 and 198 of the arms 192 and 194 are connected to electrical wires200 and 202 that emerge from an aperture 203 near the outer end portion172 of the tube 52. The other portions of the linkage 190 areelectrically insulated from the sleeve 170, the drive rod 178, and eachother. In this arrangement, the outer end portions 196 and 198 of thearms 192 and 194 are electrically connectable in the stimulator systemto function as bi-polar electrodes.

The bi-polar electrodes 196 and 198 are spaced apart from each other adistance that can be varied in a controlled manner by manualmanipulation of the scissor-action handle 160. Specifically, the handle160 is shown in a fully closed condition in FIG. 6. As the handle 160 isbeing opened, the drive rod 178 is moved longitudinally from right toleft, as viewed in FIG. 6. This actuates the linkage 190 to move theelectrodes 196 and 198 away from one another toward the fullyspaced-apart positions shown in FIG. 7. As the handle is again movedback toward the closed condition, the drive rod 178 is moved back fromleft to right, and the linkage 190 moves the electrodes back toward oneanother. A locking structure 206 on the handle 160 has a scale thatindicates the separation distance between the two electrodes 196 and198.

Each mapping probe system described above is used in a stimulator systemto facilitate the intra-operative location of nerves by NMES whilerecording the resultant signals. The user interfaces for the stimulatorsystem may include foot switch controls and graphical displays. Theinformation collected by the system may be graphically displayed duringa procedure on a computer screen or monitor.

This written description uses examples to disclose the invention,including the best mode, and also to enable a person skilled in the artto make and use the invention. The patentable scope of the invention isdefined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples, which may be availableeither before or after the application filing date, are intended to bewithin the scope of the claims if they have structural elements that donot differ from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral language of the claims.

1. A monopolar neuromuscular electrical stimulation (NMES) apparatus foruse with a cannula and a remote electrode, said apparatus comprising: alongitudinally rigid rod configured to be received and moved in thecannula throughout a range of operative positions in which inner andouter end portions of said rigid rod extend longitudinally outward fromthe inner and outer ends of the cannula; and a single electrodeconfigured to be supported as a solitary electrode on said inner endportion of said rigid rod for movement with said rigid rod through thecannula, and thereby to be moved into and out of contact with internaltest sites to apply NMES at the internal test sites in an electricalcircuit with the remote electrode upon movement of said rigid rod backand forth in the cannula; wherein said rigid rod comprises a rigid tubeand said electrode is a suction-tip electrode configured to communicatepneumatically with said rigid tube.
 2. An apparatus as defined in claim1 wherein said suction-tip electrode is part of an electrode assemblyincluding a flexible tube configured to communicate said suction-tipelectrode pneumatically with said rigid tube.
 3. An apparatus as definedin claim 1 wherein said rigid rod is sized with reference to the cannulato form a pneumatic seal between said rigid rod and the cannula whensaid rigid rod is located in the cannula in any one of said operativepositions. 4.-6. (canceled)
 7. A monopolar neuromuscular electricalstimulation (NMES) apparatus for use with a cannula and a remoteelectrode, said apparatus comprising: a longitudinally rigid rodconfigured to be received and moved in the cannula throughout a range ofoperative positions in which inner and outer end portions of said rigidrod extend longitudinally outward from the inner and outer ends of thecannula; a single electrode configured to be supported as a solitaryelectrode on said inner end portion of said rigid rod for movement withsaid rigid rod through the cannula, and thereby to be moved into and outof contact with internal test sites to apply NMES at the internal testsites in an electrical circuit with the remote electrode upon movementof said rigid rod back and forth in the cannula; and a stand-offextension configured to support said electrode on said inner end portionof said rigid rod for movement relative to said rigid rod.
 8. Anapparatus as defined in claim 7 wherein said stand-off extensionincludes a hinge.
 9. An apparatus as defined in claim 7 wherein saidinner end portion of said rigid rod is tubular and has an open innerend, and said electrode is configured to close said open inner end ofsaid rigid rod when supported on said inner end portion of said rigidrod.
 10. An apparatus as defined in claim 7 wherein said rigid rod issized with reference to the cannula to form a pneumatic seal betweensaid rigid rod and the cannula when said rigid rod is located in thecannula in any one of said operative positions.